1. Field of the Invention
This invention relates to pumps of the type known as sump pumps and utility pumps and concerns an expanded foam housing in combination with a relatively thin, metallic motor casing around which the housing is molded. The housing is of sufficient density and strength to support the motor and includes walls defining an integrally molded handle, volute and discharge passageway. Four radially oriented openings or windows in the housing expose portions of the metallic motor casing to enable the casing and thereby the motor to be cooled during operation of the pump.
2. Description of the Prior Art
Over the years, the popularity of small, portable pumps has increased as new and different uses for such pumps are brought to light. Pumps generally classified as utility pumps can be used, for example, in temporary locations for draining swimming pool covers, boats, and flooded basements. Sump pumps, on the other hand, are often very similar to utility pumps except that sump pumps are normally permanently located in a basin or sump and are provided with sensors or switches which automatically activate and deactivate the pump in accordance with the level of water. Additionally, the water inlet for sump pumps is often spaced a distance above the bottom of the pump housing to inhibit dirt and debris in the sump from being forced through the pump, while the inlet for utility pumps is somewhat lower and nomally located at the bottom of the housing so that a maximum of water can be extracted and drained from the location of use.
One type of submersible pump is disclosed in U.S. Pat. No. 3,748,066, dated July 24, 1973 and owned by the assignee of the present invention. The pump shown in U.S. Pat. No. 3,748,066 has an inner motor housing surrounding a motor and containing a quantity of dielectric oil, an outer jacket or housing which surrounds the motor housing, a motor dome to cover the motor and contain the oil, a base member having walls defining a volute and discharge passageway as well as a number of O-rings and seals which are used to preclude leakage and/or intermixing of the dielectric oil and liquids to be pumped.
While the pump disclosed in U.S. Pat. No. 3,748,066 represents a significant advance in the art for reasons which are not significant to an understanding of the present invention, there is nevertheless a need to reduce the time and expense necessary to build the pump components and assemble the same without adversely affecting the durability and longevity of the pump, especially considering the fact that utility pumps, for instance, can be moved frequently from place to place and used in hostile environments. Pumps constructed in similar fashion to the pump shown in U.S. Pat. No. 3,748,066 typically have as many as 30 to 40 separate components that are assembled by hand and as a consequence great reliance is placed upon the seals and O-rings for keeping the dielectric oil and pumped liquids in their respective places.
Oftentimes, a number of the pump housing components including the motor housing, motor dome, outer jacket and base member are comprised of a synthetic resinous material that is manufactured by an injection mold process. However, injection molding is a complex technology and requires use of heating coils in the mold to initially maintain the synthetic resinous material in a flowable condition for filling the mold. Cooling coils are also necessary in order to rapidly dissipate heat from the synthetic resinous material once the same is in place and the heating coils are deactivated. Various areas of the mold defining cavities and wall sections of different thicknesses require highly engineered and precisely positioned heating and cooling coils so that proper heat introduction, distribution and subsequent dissipation is ensured.
The electrical wires forming the windings in motors are typically insulated with a thin varnish type of material that is damaged when subjected to temperatures above, for example, 125.degree. Centigrade. As a consequence, it is not practical to form an injection-molded jacket for the pump directly around the motor in an attempt to reduce the time required for assembly, since injection molding processes are normally carried out at temperatures ranging from 200.degree.-250.degree. Centigrade. Also, the plastic material is introduced into such molds by means of screw augers or the like under pressures which are of a value sufficient to injure certain components of the motor assembly and to cause a portion of the synthetic resinous material to enter the motor bearings and areas between the rotor and stator.